For some years, such hose-shaped outer films, also called hose outer films or outer hose films, have been in practical use as parts of insert hoses during pipe rehabilitation, such as (for example) trenchless sewer pipe rehabilitation. Given its method, which is environmentally friendly and carried out with minimal expense, this type of sewer repair offers great advantages. A flexible insert hose (also called a hose liner or simply a liner) is drawn into the pipe to be rehabilitated (drawing-in method), whereas the insert hose slides over a sliding film or a so-called “pre-liner” previously laid in the sewer pipe.
With glass fiber hose liner systems with UV-curing or steam-curing, such an insert hose (hose liner) typically features one inner hose and one outer hose (inner or outer hose), between which a carrier material made of (for example) glass fibers is inserted, which carrier material is impregnated with reactive plastic resin. Thereby, the hose shape of the outer hose is obtained through the corresponding shaping and fusing of flat films. Commercial UP resins (polyester or unsaturated polyester resins), VE resins (vinyl ester resins) or EP resins (epoxy resins), for example, are used as reactive plastic resin. With UP or VE resins, the curing of the resins takes place, for example, with the assistance of photoinitiators (as radical generating agents). The curing may also take place thermally. The insert hose is inflated in the pipe until it fits against the inner pipe wall or the sliding film and/or the pre-liner, in order to subsequently cure the resin—by means of, for example, UV light from a light source slowly drawn through the pipe. Finally, the inner hose film of the insert hose is typically drawn out and removed. The layer with the carrier material and the cured resin is then exposed to the substances to be led through the pipe.
So that, during storage (that is, prior to installation in the pipe), the curing in the insert hose does not take place prematurely through the UV radiation of sunlight, it is known from WO 2013/026568 A1 to introduce a substance absorbing and/or reflecting UV radiation and, if applicable, short-wave light into an outer layer or a layer near the outer side, whereas non-silvery metal oxides, transition metal oxides and other inorganic and organic compounds may be used for this purpose. In one layer that is arranged on the other outer side of the outer film turned to the resin, an inorganic compound reflecting UV radiation, preferably a white pigment, is inserted. This measure serves to reflect UV rays that emanate from a UV source to be drawn through the pipe and has already permeated the resin, in order to increase the efficiency and speed of the curing process. However, it turns out that both the sealing and blocking effect against UV light and visible light (there, specified only for a restricted wavelength range) and that the reflection yield of this known hose-shaped outer film is still worthy of improvement.
An alternative is described in DE 297 00 236 U1, with which an external shell is metallically coated, or consists of a metal film wrapped in a helical manner around the carrier system. However, for achieving a seamless reflection, this arrangement is difficult to manage and expensive. In addition, the shell described therein always features a permeability for UV light that is still too high, by which the resin lying thereunder cannot be protected from premature curing.